Spring-stripper for use with punches,dies and the like



Dec. 23, 1969 H. s. ACHLER ETAL SPRING-STRIPPER FOR USE WITH PUNCHES,DIES AND THE LIKE Filed Dec. 21, 1967 zw .x f a 5 0 IOQWWE h a 8 1 ja A?m, 2 6 1 ad 0%; 0 Q0 2 .3 5 J I 4 3.

United States Patent 3,485,122 SPRING-STRIPPER FOR USE WITH PUNCHES,

DIES AND THE LIKE Howard S. Achler, 9750 S. Luella St., Chicago, Ill.60617, and Harold Kaufmann, 1501 Idlewild Lane, Homewood, Ill. 60430Filed Dec. 21, 1967, Ser. No. 692,591 Int. Cl. 1326f N02 US. Cl. 83-139Claims ABSTRACT OF THE DISCLOSURE An improved spring-stripper isprovided by the combination of a cylindrical spring-like sleeve ofurethane rubber with durometer-scale hardness in the range of 75-98Shore A having a stripper-disc cap of urethane rubber withdurometer-scale hardness greater than the hardness of the spring-sleeveassembled thereon by a press fit. The hardness of the cap is in therange of 100-130 Shore A and preferably is at least 10 points higher onthe Shore A scale than the hardness of the sleeve. The simplicity of apress-fit permits assembling a precise length spring-stripper at thesite of usage, since caps may be readily assembled with sleeve-1ikesprings cut to precise length from stock lengths. A bevel provided onthe inner peripheral edge of the caps flange assists in assembly.

BACKGROUND OF THE INVENTION This invention relates to an improvedspring-stripper for use in machine shops and in production operationssuch as with punches, ejectors and the like.

It has been known to use sleeves of polyurethane as springs inspring-strippers in machine shop and production operations such as withpunches, ejectors and the like. In certain prior constructions, a cuppedend member of steel or other metal has been secured to an end of thesleeve-spring by upsetting the distal end of the metal flange to causesame to bite into the peripheral wall of the sleeve-spring at a regionspaced from the bottom of the cut. Such prior constructions have, amongothers, the following deficiencies: the metal end member tends to marthe work against which the stripper abuts in stripping; the saidattachment of the end member to the sleeve-spring produces non-uniformand undesirable stresses in the sleeve-spring; the construction isrelatively expensive and fails to provide flexibility in the productionof spring-strippers of.desired size and length at the site of usage.

In other prior constructions, punch stripping has been elTected bysprings formed either of natural rubber or urethane elastomericmaterials that have been molded into cylinder or cup-shaped bodies ofpre-selected sizes with a pilot hole through the base of the cup.Primary deficiencies of such constructions are: the base of the cup maynot be hard enough to effect a proper stripping function; there is aneconomic limitation on a suppliers ability to provide all sizes ofoutside diameters, inside diameters and length of springs, and alimitation on the ability to provide for producing desired sizes andlengths of springstrippers at the site of usage.

SUMMARY OF THE INVENTION Thus, an object of this invention is to providean improved spring-stripper that is constructed of a separate urethanespring and urethane stripper-cap of different durometer hardnesses toprovide for press fit assembly and retention in assemblage, therebyaifording the greatest flexibility possible in selection of differentcombinations of outer diameter, inner diameter and length of "icesprings and permitting ready production of spring-strippers at the siteof usage.

Another object of this invention is to provide an 1mprovedspring-stripper that avoids the undesirable features of priorconstructions and which is characterized by its simplicity andinexpensiveness of construction. I

Further objects and advantages of this invention Wlll become apparent asthe following description proceeds and the features of novelty whichcharacterize this invention will be pointed out with particularity inthe claims annexed to and forming part of this specification.

A preferred embodiment of the invention is shown in the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 illustrates, partially incross-section, an assemblage of a typical punch with a spring-stripperthat embodies the invention herein;

FIGURE 2 is an enlarged cross-section view of the assembled spring andstripper/shedder-cap embodying the invention herein disclosed;

FIGURE 3 is a top plan view of the device shown in FIGURE 2;

FIGURE 4 is an exploded perspective view of the de vice of FIGURE-S 2and 3, showing a separate. spring and stripper/shedder-cap as theyappear when separated and prior to assembly;

FIGURE 5 is a view, similar to FIGURE 1, showing an assemblage usable asa shedder; and

FIGURE 6 shows still another variation of assemblage of parts hereindisclosed.

Referring now to the drawings, FIG. 1 illustrates one typicalenvironment for the spring-stripper of this invention. As shown in FIG.1, there is a typical punch installation generally indicated at 10 thatincludes a front plate- 12 and a backup plate 14, the plates beingtypically connected together and/or aligned by means of a bolt 16 and/orpin 18. The front plate 12 is bored as at 12a to receive therethroughthe shank of a headed punch pin generally indicated at 20. The punch pin20 has a head end 20a, a shank 201), a punch tip 200, and a fairedportion 20d which necks down from the shank 20b to the cylindrical punchtip 200. The. front plate 12 is provided with a counterbore 22 toreceive and seat the head 20a of the punch pin 20. Thus far what hasbeen described is well known in the art and forms no part of theinvention herein but serves to describe an environment Wherein theinvention of the spring stripper is to be used.

The spring-stripper is generally indicated at 24 and includes anelongated sleeve 26- of a synthetic rubber-like material, namely aurethane rubber with a durometerscale hardness in the range of -98 ShoreA, that serves as a spring. As a preferred example, the hardness ofspring 26 is in the range of i3 Shore A. The spring 26 is made of atough, resilient, high-modulus of urethane rubber that will withstandmore than 100,000 cycles of compression. Such a urethane rubber isavailable from Kaufmann Tool & Engineering Corp., of Chicago, 111.,under its Specification as K-167. It will be understood that the spring26 may be selected of any length and may be of any selected outer orinner diameter. It is suificient to note here that the inside diameterof the spring sleeve 26 is so selected inthe particular example heredisclosed relative to punch pin 20, that the shank 20b has what is knownas a wring fit in sleeve 26, namely that in the absence of forcestending to eifect sliding, the sleeve 26 remains positioned on and heldby slight friction between shank 20b and sleeve 26, but the fit is suchthat the sleeve 26 may he slid onto punch 20 to reach the condition ofFIG. 1.

The remainder of the spring-stripper of this invention is a cap member28 which also is formed of a rubber-like material, namely urethanerubber, but here the cap is required to be very tough and hard and isformed with a durometer-scale hardness of a selected degree greater thanthe durometer-scale hardness of the sleeve 26. The durometer-scalehardness of the cap may be in the range of 100- 130 Shore A, and as apreferred example the hardness is at least points greater than thehardness of sleevespring 26 and is in the range of 1l4l20 Shore A.

The cap 28 in its normal condition prior to assemblage is best seen inFIG. 4, or in assemblage is seen in cross section in FIG. 2. The cap 28is shaped to provide a flat disc-like portion 28a having an integralperipheral flange 28b extending transversely of portion 28a from oneside thereof. The inner dimension of the flange 23b is selected so thatit is just slightly smaller than the exterior periphery of the sleeve26. This arrangement is such that sleeve 26 and cap 28 may be assembledonly by a press fit of the parts.

The end of the annular flange 28b that is distal from the disc portion28:: of the cap 28 has a continuous peripheral chamfer or bevel 28cdefined on the inner edge. The bevel 28c assists in centering the sleeve26 with the peripheral flange 28b, and assists in the effecting of apress fit assemblage between the sleeve 26 and the cap 28.

It will be seen that both the sleeve 26 and the cap 28 are formed ofurethane rubber, with the cap being provided with a hardness greaterthan the hardness of the sleeve in an amount of at least 10 points onthe Shore A durometer scale. While the bevel 280 is preferablycontinuous along the inner periphery of the flange 28b, it will beappreciated that the bevel 280 may be in the form of segmental lengthstoward achieving the same effect.

The cap 28 is provided on the spring side of the disc portion 28athereof, which faces in the direction that the flange 281) extends fromthe disc 28a, with a countersink notch or centering recess 28d that islocated centrally of the annular flange 28b. Preferably the recess hasan included apex angle of about 118. The recess 23d serves as a guidefor a drill bit in drilling out a hole such as 30 as seen in FIG. 1through which the punch tip 200 may protrude as in a punching operation.

The simplicity and utility of the device is apparent from the foregoingdescription. The sleeve-spring 26 may be cut and/ or formed to anydesired length and size from an elongated rod or tube of urethane rubberstock of the required durometer hardness. After the desired length ofsleeve-spring 26 is available, it may be used as a spring, or ifintended for use as a stripper or shedder then caps may be provided atthe outermost end, or at both ends, if desired. Assemblage is by asimple press fit effected in a vise, or by means of an arbor press orupon first stroke of the ram, or punch as seen in FIG. 1. The press fitis such, and the nature of the urethane rubber is such, that the pressfit causes the cap 28 to squeeze the inserted end of spring 26 anddevelop retention pressure in the resilient material so as to securelymounted on and held by the sleeve 26.

The cap 28 as is may serve as a shedder, or if intended as a stripper itmay be drilled, pierced or machined to provide a central aperture 30that conforms to the contour of the punch. While in the example shown inFIGURE 1 the punch tip is cylindrical, an aperture 30 of any othercontour is intended to be disclosed herein. The spring 26 is usuallyprovided slightly longer than final intended usage, such as inch longerto compensate for permanent set which may occur during the first fewpress strokes, depending upon the percentage of deflection designed for.In preferred usage, the disc 28a of cap 28 is provided with a flatsmooth outer :face and the urethane is reinforced and molded, or cast,with randomly disposed glass fibers substantially uniformly distributedwithin the urethane rubber of the cap.

The spring-stripper of FIG. 2 is then assembled onto the shank d of apunch, and the friction developed between the sleeve 26 and the shank20b is sufficient to hold the parts assembled as seen in FIG. 1. Thenature of the urethane rubber material is such that once press fit intoposition as seen in FIG. 2, the sleeve 26 tightly holds the cap 28 andthe parts will not separate under the ordinary pressure developed by useof the punch 20. The cap 28, since it is formed of urethane rubber,operates as a stripper plate in FIGURE 1, or as a shedder as hereinafterdescribed in FIGURE 5, and at the same time avoids any marring of thesurface of the material against which the cap 28 is pressed.

The spring-stripper 24 herein disclosed will: provide for its sizeunusually high pressures because of the spring modulus of the materialof spring 26; permit close center distances because of the strength ofthe materials; provide positive stripping action; reduce and damp punchvibration; provide for simple and quick installation without set screwsor stripper bolts; prevent marring of the work against which the caps 28abut; and prevent shrapnellizing (flying into pieces) as occurs withcompetitive devices that fracture under load, thereby protecting bothdies and workers.

In FIGURE 5 there is shown another assemblage using the same parts,namely a spring-sleeve and cap assembled for use as a shedder. Theenvironment includes frame means generally indicated at 30 arranged todefine a recess, 32. A pin 34 carried by frame means 30 projects 1ntorecess 32 and carries an elongated spring-sleeve 26' whose lower end haspress fit thereon an imperforate cap 32' which serves as a shedder.

In FIGURE 6, still another assemblage is shown. The environment includesframe plate 36 carrying pin 38. The assemblage has an elongatedspring-sleeve 26" with an imperforate cap 32' press fit on its lower endand a. top cap 32" press fit on the sleeves upper end. The top cap 32"is bored at 32a for receiving therethrough the pin 38.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. An improved spring-stripper consisting of an elongated sleeve ofsynthetic rubber-like material, and a cap of rubber-like materialdefining a disc-like transverse portion and an annular flange, the capbeing assembled on one end of said elongated sleeve by a press-fitbetween said sleeve and said annular flange, the sleeve and cap bothbeing formed of urethane rubber, with the cap provided with a hardnessgreater than the hardness of the sleeve in an amount of at least 10points on the Shore A durometer scale.

2. A device as in claim 1 wherein the sleeve has a right-circularexterior periphery, and the flange on the cap has a right circularinternal periphery that is slightly smaller than the exterior peripheryof the sleeve for engaging and slightly compressing an end portion ofthe right-circular exterior periphery of the sleeve so as to retain thecap on the sleeve.

3. A device as in claim 2 wherein the end of the annular flange distalfrom said transverse wall portion has a bevel defined on the inner edgeto assist in centering the sleeve before effecting a press-fit betweensaid sleeve and cap.

4. A device as in claim 1 wherein the hardness of the sleeve is in therange of -98 Shore A on the durometer scale.

5. A device as in claim 1 wherein the hardness of the cap is in therange of -130 Shore A on the durometer scale.

6. A device as in claim 1 wherein the hardness of the sleeve is in therange of 951-3 Shore A on the durometer scale and wherein the hardnessof the cap is in the range of 114-120 Shore A on the durometer scale.

7. A device as in claim 1 wherein the sleeve is provided with a cappress fit on each end.

8. An improved stripper cap for use with an elongated, cylindricalspring sleeve of synthetic rubber-like material, said improved strippercap providing a disc-like transverse wall portion integral with anannular flange extending perpendicularly from said transverse Wallportion, the interior periphery of said annular flange being slightlysmaller than the exterior periphery of an end portion of the cylindricalsleeve, so that the cap must be press fit onto an end portion of thesleeve to assemble the stripper cap with a sleeve, said stripper capbeing formed of urethane rubber having a hardness of at least 10 pointsShore A on the durometer scale greater than the hardness of the sleeve.

9. A device as in claim 8 wherein the hardness of the cap is in therange of 100-130 Shore A on the duroineter scale.

10. A device as in claim 8 including a centering recess defined on saiddisc-like transverse wall located precisely centrally of said annularflange.

References Cited UNITED STATES PATENTS 1,934,681 11/1933 Damsel 215-41 X2,601,039 6/1952 Livingstone 222562 2,823,249 2/1958 Curtiss 21541 X2,889,089 6/1959 Herrick et al. 29450 X 3,211,035 10/1965 Whistler et a183139 3,234,835 2/1966 Archbold et a1 83-139 3,269,238 8/1966 Whistler,et al. 83-139 JAMES M. MEISTER, Primary Examiner

